The study from the Keck School of Medicine at USC shows children whose mothers lived in areas with high levels of pollution from traffic are twice as likely to develop autism, NBC Southern California reported.

"This does not say that pollution causes Autism," said Dr. Douglas Vanderbilt, with Children's Hospital Los Angeles. "What is says is that there is an association."

The study suggests nitrogen dioxide and small particles that come from traffic pollution affect the lungs and the brain.

Studies like this may pave the way, according to Vanderbilt, toward one day finding effective treatments for this mysterious disorder.

"I think it's a lot of hope because we're moving forward, and trying to understand what's causing this problem," Vanderbilt said. "How we can diagnose it and how we can treat it."

According to the Centers for Disease Control, autism now affects one in every 88 babies born in the U.S. That's a 24 percent increase over the past six years.